Testing metallic coatings



April 1930- I K. PITSCHNER 1,753,301

TEST ING METALLIC COATINGS Original Filed Bee 22, 1926 v v 0' In 01% on 0 0 g H Q a a o O Q 0 n I a o 053" a 0 1,

n a) o a u o o O a o INVENTOR Kar F1 fschner.

. Patented A r. s, 1930- UNITED STATES PATENT 0mm;

or namenronn-eomcrrcur, assrenoa 'ro Amman oaanr comm, me, A comma-10x or raw You rns'rme mar-mo coa'rmes Application filed December, 19%, Serial No. 186,510. Renewed Kay 16, 1828.

A more limited object is a 'method and This invention relates to methods and means of detecting the presence and location of minute holes in material in thin sheet form' such as metal plating, paint and similar adherent coatings and foil. The process mvolves the application of the thin sheet to a base ofa different material and utilizes the fact that certain substances are characterized by a chemical reaction onthe base which difi'ers from their chemical reaction on the sheet to be tested. The process finds its greatest utility in testing thin sheet metal or metal plating which is adherent toits base, such as electro-plating, but can be used as well for testing non-adherent sheets; the base in this instance serving merely to produce the desired diiference in reaction. In thev commerical aspect the process and method are most useful in testing nickel plating on to their application for that'purpose. It is to be understood, however, that the full scope of the invention is to be determined from the appended claims.

- It is well'known that much difliculty is experienced in metal plating, especially nickel plating on ferrous bases by reason of the fact that the plating, even in spite of extreme care,

frequently contains a considerable number of minute holes, through which minute areas of the base are exposed. .As is well known,

the exposure of these minute areas of the base, particularly a ferrous base, results in corrosion inthe vicinity ofeach hole which gradually spreads, resulting not only in an unsightly appearance oflthe product, but in defeating the object of the plating. Thesev minute holes are not visible with the unaided eye, and are with diflicult detected with a microscope. From the industrial stand-. point, therefore, some rapid factory method is needed, both for detecting the general efliciency of particular processes carried out,

and also for the elimination of defective.

products. It is the principal'object of my invention to supply the need last mentioned, and in a manner non-destructive to the article tested.

means of ap lying to the pieces to betested,

the chemicaFreagent above referred to. A 1

process and objects of the rocess may be had cm the following spec' cation, in conjunction with the accompanying drawing, in

. which,

Fig. 1 shows a strip of pa or giving indications ofpinholes throng nickel over a ferrous metal. Fig. 2 shows a stri of paper giving indications of ,pin holes ough nickel over copper over a ferrous metal.

In order'to illustrate the process of testing metal sheetson a base of a different character, the. specific use will be described in connection with nickel electroplated on a ferrous or copper base.

1 .The test is performed b applying a strip of treated aper to the sur ace of the metal to be tested a r it has been thoroughly cleaned, and the pa 1' wet with pure water. The paper may of any common stock suitable solution. This solution is termeda ferroxyl solution due to its oxidizing eifect on ferrous metals. When allowed to cool, this solution forms a jelly-like substance. This can be kept without deterioration if not ex-- posed to a strong light or the air. Before the bottle containing the solution be immersed in a hot bath to soften After t ,ese are dissolved 250 cubic centimeters of ethyl, methyl or a good grade of denatured alcohol are addedto the reagent the jelly. The reagent is then applied to one side of a sheet of good White paper in such a way that an-even coating is obtained.

The solution may be applied to the paper in any well-known manner but the preferred form is to spray the solution on the paper and then spread it with a brush having its bristles set in rubber with no iron exposed.

The surface of the metal to be tested is now cleansed free from grease, dirt or other foreign substances. The test paper is then moistened on the treated side with pure water, and spread over the surface. The location ofall holes and scratches extending from the surface through to the ferrous metal base are made visible to the eye by a coloration of the paper directlyover the hole posited on the copper, pin holes and scratches through to the copper only will be indicated by a brownish red spot, and at the same time pin holes and scratches throu 11 to the ferrous base will be shown by a eep bluespot on the same paper. 1 i

- A test sheet of this character is shown in Fig. 2, the marks 1 being of a deep blue indicating a hole through to the ferrous metal, and marks 2 being of a reddish brown color indicating the scratches or holes through to the copper. The cross mark 3 is a scratch madethrough the nickel to the copper to indicate the operation of the test.

The tests slips may be made apermanent record by painting immediately after the tests with a thin' coating of clear shellac, thereby protecting the surface from action by light and abraslon.

It is also apparent that this process may be'used for testing coatings of paint on metal bases 0r the detection of pin-holes in metal foil, the foil being placed on a bed of pure metal with whichthe solution has a chemical action and will give an obvious indication on the test slip.

It is also obvious'that theindications on the test slips do not necessarily have to be immediately 'visible but may be developed;

by a developing solution which has an action on the deposits thereby making,the indications visible. I

' I claim A 1. A process of detecting the presence of minute holes in ,material in sheet form on a base of diii'erent material, which comprises.

applying to said sheet a strip of material carrying a substance characterized by a chemical reaction on said base distinguishable from its reaction on said-sheet, said substance acting through said holes'to produce on said strip a change which differentiates chemical reaction on said base distinguishable from its reaction on said sheet, allowing said sheet to remain until said substance act-- ing through said minute holes has produced on said strip a change which differentiates the area covering and surrounding said holes from the remaining area of said strip, thereby forming on said strip after having been removed from said sheet, a legible record of the presence of said holes.

3. A process of detecting the presence of minute holesin nickel plated on a ferrous base, which comprises applying to said sheet.

a strip of material carrying a substance characterized by a chemical reaction on said base distinguishable from its reaction on said nickel, said substance acting through said holes to produce on said'strip' a change which differentiates the area thereof covering and surrounding said holes from the remaining area thereof, thereby forming alegible record of the presence of said holes.

4. A process of detecting the presenceof minute holes in a sheet of copper pl ted on a ferrous base, and a second sheet 0 vnickel plated on said copper which compri? pplying to said outer sheet a strip of material carrying a substance characterized by a chemical reaction on said base distinguisha ble from its reaction on said sheets, said substance actingv through said holes to produce on said strip a changewhich differentiates said holes. in said nickel from those in said copper and from the remaining area thereof, thereby forming a legible record of the presence of said holes in both sheets.

5. A process of detecting the presence of minute holes in nickel plated on a ferrous base, which comprises applying to said sheet a strip of material carrying a ferroxyl solu-' tion, said solution being characterized by a chemical reaction on said base distinguishable from its reaction on said nickel, said solution acting through said holes to produce on said strip a change which diiferentiatesthe area thereof covering and surrounding said holes from the remaining area thereof, thereby forming a legible record of the presence of ferrous base, and a second sheet of nickel plated on saidcopper which comprises applying to said outer sheet a strip of material carrying a ferroxyl solution, said solution being characterized by a chemical reaction on said base distinguishable from its reaction on said sheets, said solution acting through i said holes to produce on said strip a change after said strip has been removed from said sheet which differentiates the area thereof covering and surrounding said holes in said nickel from those in said copper and from the remaining areas ,thereof, thereby forming a legible record of the presence of said holes in both sheets.

7. A process of detecting the presence of minute holes in material in sheet form on a base of different material which comprises applying-to said sheet a strip of paper carrying'aferroxyl-solution,said solution being characterized by a chemical reaction on said base distinguishable fromits reaction on said sheet, said solution acting through said minute holes to produce on said strip a change which diiferentiates the area covering and surrounding said holes from the remaining to the base material whereby such reaction minute holes in material in sheet form. on a base of different material which comprises applying to said sheet a vehicle detachable therefrom and carrying a substance difi'erentially reactive to the sheet and the base where-- by such reaction with the base through the holes be distinguishable from that with the sheet, thereby producing a record of the presence and approximate area of said holes.

13. A process of detecting uncoated areas of a base provided withla coating which comprises applying to the coated surface of the bases vehicle detachable therefrom and carrying a substance reactive to the base and such reaction with the base being distinguishable from that-with the coating whereby a record will be produced ofthe presence and approximate extent of the uncoated areas of the base. 7 v

In testimony whereof, I have signed this specification.

KARL PI ISOHNER.

area of said strip, thereby forming a legible record of the presence of said holes, said fer roxyl solution comprising, in their correct proportions, parts of agar-agar, water,-so-

- diumchloride and potassium ferri cyanide,

dissolved in ethyl alcohol. I

8. A process of detecting the presence of minute holes in material in sheet form on'a base of different material, which comprises applying to'said sheet a strip of material carrying a substance characterized by a chemical reaction on said base distinguishable from its reaction on said sheet, said substance acting through said holes to produce onsaid strip a' change which differentiates the area thereof, covering and surrounding said holes from the remaining 'area thereof, thereby formin a le' "ble record of the resence of said'hol es, an a'permanent recor when said I strip has been given a coating of clear shellac after having been removed from said sheet. 9. A process of producing a record of the presence of. 110185111 material .in sheet form on a base of different material which oomprises ap lying to said sheet a vehicle detachable t erefromand carrying a substance reactive to one of said materials. 10.- A process of producing a record of the i 5:; presence of minute holes in material in sheet orm on a base of a difl'erent material which comprises applfying to said shed. a vehicle dey tachable there m and carrying a substance difierentiallyreactive to mau -ide 60 spectively. 11. A process minute holes in material in sheet form. .on a base of difier'ent material which con! rises v a plyingto said sheet a vehicle deta ble '65 t erefrom andicarrying a substance'reactive of detecting the presence of I 

